1. Technical Field
The present invention relates to a horizontal multi-joint robot and a robot.
2. Related Art
JP-A-2009-226567 describes a horizontal multi-joint robot (SCARA robot) according to the related art. The horizontal multi-joint robot described in JP-A-2009-226567 has a pedestal, a first arm mounted on the pedestal so that the first arm can swivel (i.e., turn, rotate or pivot), a second arm mounted on the first arm so that the second arm can swivel, a work head mounted on the second arm, and a harness (duct) with one side thereof mounted on the pedestal and the other side thereof mounted on the second arm. Wires and pipes connected to a second arm drive motor and a work head drive motor are housed inside the harness. Such a horizontal multi-joint robot of JP-A-2009-226567 has, for example, the following two problems.
The first problem is that driving of the horizontal multi-joint robot causes the harness to shake and thus generates unwanted vibration. Specifically, in the horizontal multi-joint robot of JP-A-2009-226567, the root of the harness on the pedestal side is shifted from the axis of the first arm and the root of the harness on the second arm side is shifted from the axis of the second arm. Therefore, when the first and second arms swivel, the distance between both roots of the harness changes and this change causes the harness to deform and vibrate unnecessarily. Also, the swiveling of the first and second arms causes the harness to twist and vibrate unnecessarily. Such unnecessary vibration of the harness causes deterioration in the vibration damping of the horizontal multi-joint robot (increases the time required for the vibration to subside to a predetermined magnitude).
The second problem is that the horizontal multi-joint robot is increased in size. Specifically, the harness has a large height since both ends of the harness extend directly upward so as to coincide with the axes of the first and second arms. Therefore, a large space is required to place the harness which increases the size of the horizontal multi-joint robot.